System and method for providing services

ABSTRACT

A system for providing services, including: a plurality of slave device for issuing respective request message; and at least a master device processing the request message in response to the respective request message to provide a response message to one of the plurality of slave device, which issued the request message. The master device recognizes a priority-related information of the request message for processing the request message. The priority-related information includes: a first information indicating whether the request message is first received or has been received in the past but rejected for processing; and a second information indicating a receipt sequence of the request message.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a system and a method for providing services to plural clients, and more particularly to a system and a method for allowing a server or a service-providing device to provide respective services to plural clients or service-requesting devices coupled to the server or the service-providing device through an inter-coupling medium or an inter-coupling network in accordance with respective requests from the plural clients or the service-requesting devices, without causing any undesirable stubbation or deadlock situation in which processing to any request by the server or the service-providing device is suspended.

[0003] 2. Description of the Related Art

[0004] A multi-processor system includes at least a service-providing device as a server and a plurality of service-requesting device as clients, which are coupled to each other through an inter-coupling network. Japanese laid-open patent publication No. 11-219343 discloses utilization of a conventional technique for processing plural requests with coherency of data issued from the plurality of service-requesting device without causing any undesirable stubbation or deadlock situation in which processing to any request by the server or the service-providing device is suspended.

[0005] The service-providing device as the server will hereinafter be appreciated as a master device, whilst the plural service-requesting devices as the clients will hereinafter be appreciated as slave devices. The term “issued request number” will herein be defined to be the number of requests as issued from the slave device but still remain outstanding.

[0006] The master device included in the multi-processor system disclosed in the above Japanese publication further includes a first-in first-out (FIFO) buffer which receives and holds all of the requests issued from all of the plural slave devices, so that if the master device just received one or more additional requests in addition to the presence of a currently-processed request which was past received, then the master device saves the one or more additional requests to the buffer, regardless of whether or not further one or more past-received requests have also been saved in the buffer.

[0007] The master device provides respective priority to the saved request in the buffer, so that after the current processing to the currently-processed request has been completed, then the master device will process the saved request in the sequence of the given priority. If the buffer has already held one or more saved requests, then the master device may optionally give a lower priority to the just-received request than those of all of the above one or more saved requests already held by the buffer. If the buffer has no saved request, then the master device will, of course, promptly process the just-received request without saving the same into the buffer.

[0008] The buffer, allowing the additional request to the currently-processed request to be saved therein, may contribute to prevent the undesirable stubbation or deadlock situation. The necessary size or capacity of the buffer depends on the number of the slave devices and, if any, possible estimations for the respective issued request numbers. It is generally appreciated that a large number of the slave devices needs a large size or capacity of the buffer.

[0009] In the above circumstances, the developments of a novel system and a novel method for providing services to plural clients free from the above problems are desirable.

SUMMARY OF THE INVENTION

[0010] Accordingly, it is an object of the present invention to provide a novel system for providing services to plural clients free from the above problems.

[0011] It is a further object of the present invention to provide a novel system for allowing a service-providing device as a server to provide respective services to plural service-requesting devices as clients accessible thereto in accordance with respective requests from the service-requesting devices, without causing any undesirable stubbation or deadlock situation, even the service-providing device is free of any large size buffer.

[0012] It is a still further object of the present invention to provide a novel method for providing services to plural clients free from the above problems.

[0013] It is yet a further object of the present invention to provide a novel system for allowing a service-providing device as a server to provide respective services to plural service-requesting devices as clients accessible thereto in accordance with respective requests from the service-requesting devices, without causing any undesirable stubbation or deadlock situation, even the service-providing device is free of any large size buffer.

[0014] The present invention provides a system for providing services, including: a plurality of slave device for issuing respective request message; and at least a master device allowing respective access from the plurality of slave device and processing the request message in response to the respective request message in order to provide a response message to one of the plurality of slave device, which issued the request message, wherein the master device is adopted to recognize a priority-related information of the request message for processing the request message, and the priority-related information includes: a first information indicating whether the request message is first received or has been received in the past but rejected for processing; and a second information indicating a receipt sequence of the request message.

[0015] Since the priority level depend on the first receiving time or the receipt sequence of the request message which have been rejected by the master device due to its busy state or lower priority level than that of one or more other request messages, this may prevents any undesirable stubbation or deadlock situation in which processing to the request message by the master device is suspended, without using any buffer in the master device.

[0016] The above and other objects, features and advantages of the present invention will be apparent from the following descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

[0018]FIG. 1 is a block diagram illustrative of a novel service system in accordance with the first embodiment of the present invention.

[0019]FIG. 2 is a block diagram illustrative of an internal configuration of each of the slave devices coupled to an inter-coupling network in the service system of FIG. 1.

[0020]FIG. 3 is a block diagram illustrative of an internal configuration of the master devices coupled to the inter-coupling network in the service system of FIG. 1.

[0021]FIG. 4A is a diagram illustrative of a format of the request message in the system of FIG. 1.

[0022]FIG. 4B is a diagram illustrative of a format of the response message in the system of FIG. 1.

[0023]FIG. 5 is a table illustrative of operations of the request-receiving unit included in the master device of FIG. 3.

[0024]FIGS. 6 and 7 are associated flow charts illustrative of the operations of the request-receiving unit included in the master device of FIG. 3.

[0025]FIG. 8 is a flow chart illustrative of the request-issuing operations of the request transmitting unit included in the slave device of FIG. 2.

[0026]FIG. 9 is a flow chart illustrative of the response-receiving operations of the response-receiving unit included in the slave device of FIG. 2.

[0027]FIG. 10 is a block diagram illustrative of a novel service system in accordance with the modified embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] A first aspect of the present invention is a system for providing services, including: a plurality of slave device for issuing respective request message; and at least a master device allowing respective access from the plurality of slave device and processing the request message in response to the respective request message in order to provide a response message to one of the plurality of slave device, which issued the request message, wherein the master device is adopted to recognize a priority-related information of the request message for processing the request message, and the priority-related information includes: a first information indicating whether the request message is first received or has been received in the past but rejected for processing; and a second information indicating a receipt sequence of the request message.

[0029] Since the priority level depend on the first receiving time or the receipt sequence of the request message which have been rejected by the master device due to its busy state or lower priority level than that of one or more other request messages, this may prevents any undesirable stubbation or deadlock situation in which processing to the request message by the master device is suspended, without using any buffer in the master device.

[0030] It is preferable that the master device further includes: a process-deciding unit for recognizing the priority-related information to decide, whether the request message should promptly be processed or be rejected, with reference to the priority-related information; a processing unit for processing the request message; and a response unit for issuing the response message together with the second information and a third information indicating whether the request message has been processed or rejected.

[0031] It is further preferable that each of the plurality of slave device further includes: a request issuing unit for issuing the request message; and a response receiving unit for receiving the response message together with the second information and the third information and requesting the request issuing unit to re-issue the request message if the third information indicates that the request message has been rejected.

[0032] It is also preferable that the processing unit issues, to the process-deciding unit, a fourth information indicating whether the processing unit is in an acceptable state which allows the processing unit to promptly process the request message or in an unacceptable state which inhibits the processing unit to promptly process the request message, so that the process-deciding unit decides, whether the request message should promptly be processed or be rejected, with reference to the fourth information in addition to the priority-related information.

[0033] It is further preferable that the process-deciding unit is adopted to hold therein a reservation number indicating a reservation order and a service number indicating a service order for the request message separately from the request message and the response message.

[0034] It is further more preferable that the first information comprises a retry flag, the second information comprises a retry identification number, and the third information comprises a response command.

[0035] It is moreover preferable that the retry identification number, the reservation number and the service number comprise the same bit number.

[0036] It is further more preferable that the process-deciding unit sends the request message to the processing unit for allowing the processing unit to process the request message and requests the response unit to issue the response message together with the third information indicating that the request message has been processed, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is identical with the service number.

[0037] The process-deciding unit sets the response message with a retry identification number identical with the reservation number and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is not identical with the service number.

[0038] The process-deciding unit sets the response message with a retry identification number identical with the retry identification number attached to the request message and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is not identical with the service number.

[0039] The process-deciding unit sends the request message to the processing unit for allowing the processing unit to process the request message and requests the response unit to issue the response message together with the third information indicating that the request message has been processed as well as makes an increment to the service number, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is identical with to the service number.

[0040] The process-deciding unit sets the response message with a retry identification number identical with the reservation number and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the unacceptable state, and the retry flag indicates that the request message is first received.

[0041] The process-deciding unit sets the response message with a retry identification number identical with the retry identification number attached to the request message and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the unacceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing.

[0042] It is also preferable that the reservation number and the service number comprise the same bit number, and the retry identification number comprises a less bit number than the reservation number and the service number.

[0043] It is further preferable that the process-deciding unit sends the request message to the processing unit for allowing the processing unit to process the request message and requests the response unit to issue the response message together with the third information indicating that the request message has been processed, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is identical with to the service number.

[0044] The process-deciding unit sets the response message with a retry identification number identical with corresponding higher significant bits of the reservation number to the less bit number of the retry identification number, and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is not identical with the service number.

[0045] The process-deciding unit sets the response message with a retry identification number identical with the retry identification number attached to the request message and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is not identical with corresponding higher significant bits of the service number to the less bit number of the retry identification number.

[0046] The process-deciding unit sends the request message to the processing unit for allowing the processing unit to process the request message and requests the response unit to issue the response message together with the third information indicating that the request message has been processed as well as makes an increment to the service number, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is identical with corresponding higher significant bits of the service number.

[0047] The process-deciding unit sets the response message with a retry identification number identical with the corresponding higher significant bits of the reservation number and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the unacceptable state, and the retry flag indicates that the request message is first received.

[0048] The process-deciding unit sets the response message with a retry identification number identical with the retry identification number attached to the request message and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the unacceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing.

[0049] It is preferable that the at least master device comprises a plurality of master device.

[0050] It is further preferable that the slave device is adopted to select one of the plurality of master device for issuing the message request at first time to the selected one of the plurality of master device, and also to re-issue the message request to the selected one of the plurality of master device if the request message has been rejected by the selected one of the plurality of master device.

[0051] A second aspect of the present invention is a system for providing services, including: a plurality of slave device for issuing respective request message; and at least a master device allowing respective access from the plurality of slave device and processing the request message in response to the respective request message in order to provide a response message to one of the plurality of slave device, which issued the request message, wherein the master device is adopted to give a priority-related information to the response message in response to the request message if the master device rejects the request message without processing the request message, and the priority-related information includes: a first information indicating whether the request message is first received or has been received in the past but rejected for processing; and a second information indicating a receipt sequence of the request message.

[0052] Since the priority level depend on the first receiving time or the receipt sequence of the request message which have been rejected by the master device due to its busy state or lower priority level than that of one or more other request messages, this may prevents any undesirable stubbation or deadlock situation in which processing to the request message by the master device is suspended, without using any buffer in the master device.

[0053] It is preferable that the master device further includes: a process-deciding unit for recognizing the priority-related information to decide, whether the request message should promptly be processed or be rejected, with reference to the priority-related information; a processing unit for processing the request message; and a response unit for issuing the response message together with the second information and a third information indicating whether the request message has been processed or rejected.

[0054] It is preferable that each of the plurality of slave device further includes: a request issuing unit for issuing the request message; and a response receiving unit for receiving the response message together with the second information and the third information and requesting the request issuing unit to re-issue the request message if the third information indicates that the request message has been rejected.

[0055] It is also preferable that the processing unit issues, to the process-deciding unit, a fourth information indicating whether the processing unit is in an acceptable state which allows the processing unit to promptly process the request message or in an unacceptable state which inhibits the processing unit to promptly process the request message, so that the process-deciding unit decides, whether the request message should promptly be processed or be rejected, with reference to the fourth information in addition to the priority-related information.

[0056] It is further preferable that the process-deciding unit is adopted to hold therein a reservation number indicating a reservation order and a service number indicating a service order for the request message separately from the request message and the response message.

[0057] It is further more preferable that the first information comprises a retry flag, the second information comprises a retry identification number, and the third information comprises a response command.

[0058] It is moreover preferable that the retry identification number, the reservation number and the service number comprise the same bit number.

[0059] It is still more preferable that the process-deciding unit sends the request message to the processing unit for allowing the processing unit to process the request message and requests the response unit to issue the response message together with the third information indicating that the request message has been processed, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is identical with the service number.

[0060] The process-deciding unit sets the response message with a retry identification number identical with the reservation number and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is not identical with the service number.

[0061] The process-deciding unit sets the response message with a retry identification number identical with the retry identification number attached to the request message and requests the response unit to issue the responsive message together with the retry identification number and the third information indicating that the request message has been rejected, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is not identical with the service number.

[0062] The process-deciding unit sends the request message to the processing unit for allowing the processing unit to process the request message and requests the response unit to issue the response message together with the third information indicating that the request message has been processed as well as makes an increment to the service number, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is identical with to the service number.

[0063] The process-deciding unit sets the response message with a retry identification number identical with the reservation number and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the unacceptable state, and the retry flag indicates that the request message is first received.

[0064] The process-deciding unit sets the response message with a retry identification number identical with the retry identification number attached to the request message and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the unacceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing.

[0065] It is also preferable that the reservation number and the service number comprise the same bit number, and the retry identification number comprises a less bit number than the reservation number and the service number.

[0066] It is further preferable that the process-deciding unit sends the request message to the processing unit for allowing the processing unit to process the request message and requests the response unit to issue the response message together with the third information indicating that the request message has been processed, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is identical with to the service number.

[0067] The process-deciding unit sets the response message with a retry identification number identical with corresponding higher significant bits of the reservation number to the less bit number of the retry identification number, and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is not identical with the service number.

[0068] The process-deciding unit sets the response message with a retry identification number identical with the retry identification number attached to the request message and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is not identical with corresponding higher significant bits of the service number to the less bit number of the retry identification number.

[0069] The process-deciding unit sends the request message to the processing unit for allowing the processing unit to process the request message and requests the response unit to issue the response message together with the third information indicating that the request message has been processed as well as makes an increment to the service number, if the fourth information indicates that the processing unit is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is identical with corresponding higher significant bits of the service number.

[0070] The process-deciding unit sets the response message with a retry identification number identical with the corresponding higher significant bits of the reservation number and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the unacceptable state, and the retry flag indicates that the request message is first received.

[0071] The process-deciding unit sets the response message with a retry identification number identical with the retry identification number attached to the request message and requests the response unit to issue the response message together with the retry identification number and the third information indicating that the request message has been rejected, without sending the request message to the processing unit, if the fourth information indicates that the processing unit is in the unacceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing.

[0072] It is also preferable that the at least master device comprises a plurality of master device.

[0073] It is further preferable that the slave device is adopted to select one of the plurality of master device for issuing the message request at first time to the selected one of the plurality of master device, and also to re-issue the message request to the selected one of the plurality of master device if the request message has been rejected by the selected one of the plurality of master device.

[0074] A third aspect of the present invention is a method of controlling a system for providing services including: a plurality of slave device for issuing respective request message; and at least a master device allowing respective access from the plurality of slave device and processing the request message in response to the respective request message in order to provide a response message to one of the plurality of slave device, which issued the request message, wherein the method includes: recognizing a priority-related information of the request message for processing the request message, where the priority-related information includes: a first information indicating whether the request message is first received or has been received in the past but rejected for processing; and a second information indicating a receipt sequence of the request message.

[0075] Since the priority level depend on the first receiving time or the receipt sequence of the request message which have been rejected by the master device due to its busy state or lower priority level than that of one or more other request messages, this may prevents any undesirable stubbation or deadlock situation in which processing to the request message by the master device is suspended, without using any buffer in the master device.

[0076] It is preferable that the at least master device decides whether the request message should promptly be processed or be rejected, with reference to the priority-related information; and the at least master device processes the request message; and the at least master device issues the response message together with the second information and a third information indicating whether the request message has been processed or rejected.

[0077] It is preferable that each of the plurality of slave device issues the request message; and each of the plurality of slave device receives the response message together with the second information and the third information and re-issues the request message if the third information indicates that the request message has been rejected.

[0078] It is preferable that the at least master device holds a fourth information indicating whether the at least master device is in an acceptable state which allows the at least master device to promptly process the request message or in an unacceptable state which inhibits the at least master device to promptly process the request message, so that the at least master device decides, whether the request message should promptly be processed or be rejected, with reference to the fourth information in addition to the priority-related information.

[0079] It is preferable the at least master device holds therein a reservation number indicating a reservation order and a service number indicating a service order for the request message separately from the request message and the response message.

[0080] It is preferable that the first information comprises a retry flag, the second information comprises a retry identification number, and the third information comprises a response command.

[0081] It is preferable that the retry identification number, the reservation number and the service number comprise the same bit number.

[0082] It is preferable that the at least master device processes the request message and issues the response message together with the third information indicating that the request message has been processed, if the fourth, information indicates that the at least master device is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is identical with the service number.

[0083] The at least master device sets the response message with a retry identification number identical with the reservation number and requests the response unit and issues the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without processing the request message, if the fourth information indicates that the at least master device is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is not identical with the service number.

[0084] The at least master device sets the response message with a retry identification number identical with the retry identification number attached to the request message and issues the response message together with the retry identification number and the third information indicating that the request message has been rejected, without processing the request message, if the fourth information indicates that the at least master device is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is not identical with the service number.

[0085] The at least master device processes the request message and issues the response message together with the third information indicating that the request message has been processed as well as makes an increment to the service number, if the fourth information indicates that the at least master device is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is identical with to the service number.

[0086] The at least master device sets the response message with a retry identification number identical with the reservation number and issues the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as makes an increment to the reservation number, without processing the request message, if the fourth information indicates that the at least master device is in the unacceptable state, and the retry flag indicates that the request message is first received.

[0087] The at least master device sets the response message with a retry identification number identical with the retry identification number attached to the request message and issues the response message together with the retry identification number and the third information indicating that the request message has been rejected, without processing the request message, if the fourth information indicates that the at least master device is in the unacceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing.

[0088] It is preferable that the reservation number and the service number comprise the same bit number, and the retry identification number comprises a less bit number than the reservation number and the service number.

[0089] It is preferable that the at least master device processes the request message and issues the response message together with the third information indicating that the request message has been processed, if the fourth information indicates that the at least master device is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is identical with to the service number.

[0090] The at least master device sets the response message with a retry identification number identical with corresponding higher significant bits of the reservation number to the less bit number of the retry identification number, and issues the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as to make an increment to the reservation number, without processing the request message, if the fourth information indicates that the at least master device is in the acceptable state, and the retry flag indicates that the request message is first received, and the reservation number is not identical with the service number.

[0091] The at least master device sets the response message with a retry identification number identical with the retry identification number attached to the request message and issues the response message together with the retry identification number and the third information indicating that the request message has been rejected, without processing the request message, if the fourth information indicates that the at least master device is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is not identical with corresponding higher significant bits of the service number to the less bit number of the retry identification number.

[0092] The at least master device processes the request message and issues the response message together with the third information indicating that the request message has been processed as well as makes an increment to the service number, if the fourth information indicates that the at least master device is in the acceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing, and the retry identification number is identical with corresponding higher significant bits of the service number.

[0093] The at least master device sets the response message with a retry identification number identical with the corresponding higher significant bits or the reservation number and issues the response message together with the retry identification number and the third information indicating that the request message has been rejected as well as to make an increment to the reservation number, without processing the request message, if the fourth information indicates that the at least master device is in the unacceptable state, and the retry flag indicates that the request message is first received.

[0094] The at least master device sets the response message with a retry identification number identical with the retry identification number attached to the request message and issues the response message together with the retry identification number and the third information indicating that the request message has been rejected, without processing the request message, if the fourth information indicates that the at least master device is in the unacceptable state, and the retry flag indicates that the request message has been received in the past but rejected for processing.

[0095] It is preferable that if the at least master device comprises a plurality of master device, one of the plurality of master device is selected by the slave device for issuing the message request at first time to the selected one of the plurality of master device, and also for re-issuing the message request to the selected one of the plurality of master device if the request message has been rejected by the selected one of the plurality of master device.

FIRST EMBODIMENT

[0096] A first embodiment according to the present invention will be described in detail with reference to the drawings. The service system includes at least a service-providing device as a server and a plurality of service-requesting device as clients, which are coupled to each other through any available coupling medium which allow bidirectional accesses between the at least service-providing device and the plurality of service-requesting device.

[0097] In the following description, it is assumed that the service-providing providing device as a server comprises a master device, and the plurality of service-requesting device as clients comprise a set of slave devices as well as the coupling medium comprises an inter-coupling network which provides an inter-coupling between the master device and the slave devices.

[0098]FIG. 1 is a block diagram illustrative of a novel service system in accordance with the first embodiment of the present invention. The service system includes a master device 3 as a server for providing services and a plurality of slave devices 1-1, 1-2, - - - 1-n, as clients for requesting the master device 3 to provide the services in response to the issued requests, wherein the plurality of slave devices 1-1, 1-2, - - - 1-n are coupled to the master device 3 through an inter-coupling network 2. The plurality of slave devices 1-1, 1-2, - - - 1-n have a uniform or common internal configuration,

[0099]FIG. 2 is a block diagram illustrative of an internal configuration of each of the slave devices coupled to an inter-coupling network in the service system of FIG. 1. The slave device 1 further includes a request transmitting unit 11, which transmits one or more request-messages through the inter-coupling network 2 to the master device 3, and a response-receiving unit 12, which receives one or more response-messages from the master device 3, wherein the response-message includes a service content and a response command value which indicates whether the master device accepted or rejected the request. If the response command value indicates the request-acceptance by the master device 3, then the response-receiving unit 12 sends a request-enable signal to the request transmitting unit 11, so that the request transmitting unit 11 is enabled to transmit a further request-massage. If the response command value indicates the request-rejection by the master device 3, then the response-receiving unit 12 sends a request-retry signal to the request transmitting unit 11, so that the request transmitting unit 11 retry to transmit the once-rejected request-massage to the master device 3. It is assumed that the each slave device is capable of issuing the maximum number “k_(i)” of the requests.

[0100]FIG. 3 is a block diagram illustrative of an internal configuration of the master devices coupled to the inter-coupling network in the service system of FIG. 1. The master device 3 further includes a processing unit 32 which processes the received requests, a request-receiving unit 31 and a response-transmitting unit 33. The request-receiving unit 31 receives a request transmitted through the inter-coupling network 2 from one of the plurality of slave device 1, and then requests the processing unit 32 for processing the received request. The processing unit 32 determines whether the just-received request is acceptable for prompt processing or unacceptable.

[0101] If the just-received request is acceptable for prompt processing, then the processing unit 32 processes the request to generate a response message and sends the response message with a first state “0” of a busy signal to the response-transmitting unit 33, so that the response-transmitting unit 33 receives the response message with the first state “0” of the busy signal and sends the response message with the first state “0” of the busy signal, which indicates the master device is prepared to accept any further request, whereby the response-transmitting unit 33 transmits the response message together with the response command corresponding to the first state “0” of the busy signal through the inter-coupling network 2 to the slave device 1.

[0102] If the just-received request is unacceptable and rejected for prompt processing, then the processing unit 32 does not process the request and sends a second state “1” of the busy signal, which indicates the master device is busy and placed in the currently-processing state which does not accept no further request, to the response-transmitting unit 33, so that the response-transmitting unit 33 sends the response command corresponding to the second state “1” of the busy signal through the inter-coupling network 2 to the slave device 1, so that the slave device 1 may retry to transmit the once-rejected request.

[0103] The request-receiving unit 31 holds reservation numbers and service numbers, each of which may be generated by using a ring-counter which is operable to count the number not less than “m”[m=Σk_(i)(i=0−n−1)]. In this embodiment, the request-receiving unit 31 includes a ring-counter of j-bits (m≦2i), wherein an initial value is “0”.

[0104] The inter-coupling network 2 allows transmissions of the request massages from the slave devices 1-1, 1-2, - - - 1-n to the master device 3 as well as transmissions of the response massages from the master device 3 to the slave devices 1-1, 1-2, - - -1-n.

[0105]FIG. 4A is a diagram illustrative of a format of the request message in the system of FIG. 1. FIG. 4B is a diagram illustrative of a format of the response message in the system of FIG. 1. A request message 50 issued from the slave devices 1-1, 1-2, - - - 1-n to the master device 3 includes a retry flag 51, a retry identification 52 and a request information 53 which includes a request content. A response message 60 issued from the master device 3 to the slave device 1 includes a response command 61, a retry identification 62 and a request information 63 which includes a request content.

[0106]FIG. 5 is a table illustrative of operations of the request-receiving unit included in the master device of FIG. 3. FIGS. 6 and 7 are associated flow charts illustrative of the operations of the request-receiving unit included in the master device of FIG 3. FIG. 8 is a flow chart illustrative of the request-issuing operations of the request transmitting unit included in the slave device of FIG. 2. FIG. 9 is a flow chart illustrative of the response-receiving operations of the response-receiving unit included in the slave device of FIG. 2. The overall operations of the system of this embodiment will hereinafter be described with reference to FIGS. 1-9.

[0107] In the step S21 of FIG. 8, the slave device 1-1 issues a new request. In the step S22 of FIG. 8, the request transmitting unit 11 sets the retry flag 51 at “0” to generate a request message 50 and transmits the request message 50 through the inter-coupling network 2 to the master device 3. The issued request message 50 will hereinafter be referred as “request [Ra]”.

[0108] In the steps S1 and S2 of FIG. 6, it is assumed that at the time when the request-receiving unit 31 of the master device 3 receives the request [Ra], the busy signal, the service number and the reservation number take initial value “0” respectively.

[0109] In the step S2 of FIG. 6 and the steps S6 and S7 of FIG. 7, the busy signal is “0”, the retry flag is “0” and the service number and the reservation number take the same value “0”. In the step S8 of FIG. 7, the request [Ra] is transmitted from the request-receiving unit 31 to the processing unit 32. The processing unit 32 receives the request [Ra] and enters into the processing state, during which the busy signal is maintained at “1”, which indicates the processing unit 32 of the master device 3 is busy and placed in the currently-processing state which does not accept no further request.

[0110] After the processing unit 32 completes the processings to the request [Ra], then the processing unit 32 sends the response-transmitting unit 33 a request for transmitting the request-acceptance. After the response-transmitting unit 33 received the request for transmitting the request-acceptance, then the processing unit 32 sets the busy signal at “0” which indicates the processing unit 32 of the master device 3 is prepared to accept any further request.

[0111] Upon receipt of the request for transmitting the request-acceptance, the response-transmitting unit 33 generates a response message 60 including the response command 61 of “0” which indicates that any further request is acceptable to the master device 3 and that the request [Ra] has been processed and transmits the response message 60 through the inter-coupling network 2 to the slave device 1-1 for giving the slave device 1-1 a notice to the effect that the request [Ra] has been processed by the master device 3 and any further request is acceptable to the master device 3.

[0112] In the step S31 of FIG. 9, the response-receiving unit 12 of the slave device 1-1 receives the response message 60 including the response command 61 of “0”. In the step S32 of FIG. 9, the response-receiving unit 12 sends a request-enable signal to the request transmitting unit 11 for enabling the request transmitting unit 11 to issue or transmit any further request.

[0113] During the processings to the request [Ra] by the processing unit 32, the busy signal is maintained at “1” which indicates that the processing unit 32 is busy and placed in the currently-processing state which does not accept no further request. It is assumed that during the busy state “1” of the busy signal, the slave device 1-2 issues another request message 50 which will hereinafter be referred to as “request [Rb], and wherein the retry flag is set at “0”. In the step S1 of FIG. 6, the request-receiving unit 31 receives the request [Rb], whilst in the steps S2 and S3 of FIG. 6, the busy signal is “1” and the retry flag is “0”. The processing unit 32 sends the response-transmitting unit 33 a request for issuing the notice of rejection to the request [Rb], wherein the retry identification 62 becomes “0” identical with the current reservation number “0”, and further the current reservation number “0” is incremented to “1” in the step S5 of FIG. 6.

[0114] The response-transmitting unit 33 receives the request for issuing the notice of rejection to the request [Rb], and transmits the response message 60 including the retry identification 62 at “0” and the response command 61 at “1” through the inter-coupling network 2 to the slave device 1-2 which had issued the rejected request [Rb].

[0115] In the step S31 of FIG. 9, the response-receiving unit 12 of the slave device 1-2 receives the response message 60 including the retry identification 62 at “0” and the response command 61 at “1” which indicates that the request [Rb] was rejected by the master device 3. In the step S33 of FIG. 9, the response-receiving unit 12 sends the request transmitting unit 11 a request for re-transmitting the request [Rb]. The request transmitting unit 11 receives the request for re-transmitting the request [Rb] from the response-receiving unit 12. In the steps S23 and S24 of FIG. 8, the request transmitting unit 11 sets the retry flag 51 at “1” and the retry identification 52 at “0” in accordance with “0” of the retry identification 62 included in the received response message 60. The request transmitting unit 11 re-transmits or re-issues the request [Rb] through the inter-coupling network 2 to the master device 3.

[0116] After the processing to the prior request [Ra] by the processing unit 32 of the master device 3 has been completed, then the processing unit 32 sets the busy signal at “0”. It is assumed that the request-receiving unit 31 holds the reservation number “1” and the service number “0”, and further the slave device 1-3 issues still another request message 50 which will hereinafter be referred to as “request [Rc]”, wherein the request [Rc] includes the retry flag “0”. The request [Rc] is also transmitted through the inter-coupling network 2 to the master device 3.

[0117] In the step S1 of FIG. 6, the request-receiving unit 31 of the master device 3 receives the request [Rc]. In the step S2 of FIG. 6 and the steps S6 and S10 of FIG. 7, the busy signal is “0”, the retry flag is “0” and the service number and the reservation number take different values “0” and “1” respectively. In the step S12 of FIG. 7, the processing unit 32 sends the response-transmitting unit 33 a request for issuing the notice of rejection to the request [Rc], wherein the retry identification 62 becomes identical with the current reservation number “1”, and further the current reservation number “1” is incremented to “2” in the step S12 of FIG. 7.

[0118] The response-transmitting unit 33 receives the request for issuing the notice of rejection to the request [Rc], and transmits the response message 60 including the retry identification 62 at “1” and the response command 61 at “1” through the inter-coupling network 2 to the slave device 1-3 which had issued the rejected request [Rc].

[0119] In the step S31 of FIG. 9, the response-receiving unit 12 of the slave device 1-3 receives the response message 60 including the retry identification 62 at “1” and the response command 61 at “1” which indicates that the request (Rc) was rejected by the master device 3. In the step S33 of FIG. 9, the response-receiving unit 12 sends the request transmitting unit 11 a request for re-transmitting the request [Rc]. The request transmitting unit 11 receives the request for re-transmitting the request [Rc] from the response-receiving unit 12. In the steps S23 and S24 of FIG. 8, the request transmitting unit 11 sets the retry flag 51 at “1” and the retry identification 52 at “1” in accordance with “1” of the retry identification 62 included in the received response message 60. The request transmitting unit 11 re-transmits or re-issues the request [Rc] through the inter-coupling network 2 to the master device 3.

[0120] In the step S1 of FIG. 6, the request-receiving unit 31 of the master device 3 receives the request [Rc] re-issued. In the step S2 of FIG. 6 and the steps S6 and S7 of FIG. 7, the busy signal is “0”, the retry flag is “0” and the service number and the reservation number take different values “0” and “1” respectively. In the step S9 of FIG. 7, the processing unit 32 sends the response-transmitting unit 33 a request for issuing the notice of rejection to the request [Rc], wherein the retry identification 62 becomes identical with the current reservation number “1”, and further the current reservation number “1” is incremented to “2” in the step S12 of FIG. 7.

[0121] The response-transmitting unit 33 receives the request for issuing the notice of rejection to the request [Rc], and transmits the response message 60 including the retry identification 62 at “1” and the response command 61 at “1” through the inter-coupling network 2 to the slave device 1-3 which had issued the rejected request [Rc].

[0122] In the step S31 of FIG. 9, the response-receiving unit 12 of the slave device 1-3 receives the response message 60 including the retry identification 62 at “1” and the response command 61 at “1” which indicates that the request [Rc] was rejected by the master device 3. In the step S33 of FIG. 9, the response-receiving unit 12 sends the request transmitting unit 11 a request for re-transmitting the request [Rc]. The request transmitting unit 11 receives the request for re-transmitting the request [Rc] from the response-receiving unit 12. In the steps S23 and S24 of FIG. 8, the request transmitting unit 11 sets the retry flag 51 at “1” and the retry identification 52 at “1” in accordance with “1” of the retry identification 62 included in the received response message 60. The request transmitting unit 11 re-transmits or re-issues the request [Rc] through the inter-coupling network 2 to the master device 3.

[0123] In the step S1 of FIG. 6, the request-receiving unit 31 of the master device 3 receives the request [Rb] re-issued from the slave device 1-2. In the step S2 of FIG. 6 and the steps S6 and S7 of FIG. 7, the busy signal is “0”, the retry flag is “1” and the service number and the reservation number take the same value “0”. In the step S8 of FIG. 7, the request [Rb] is transmitted from the request-receiving unit 31 to the processing unit 32. The processing unit 32 receives the request [Rb] and enters into the processing state, during which the busy signal is maintained at “1”, which indicates the processing unit 32 of the master device 3 is busy and placed in the currently-processing state which does not accept no further request. The current service number “0” is incremented to “1”.

[0124] After the processing unit 32 completes the processings to the request [Rb], then the processing unit 32 sends the response-transmitting unit 33 a request for transmitting the request-acceptance. After the response-transmitting unit 33 received the request for transmitting the request-acceptance, then the processing unit 32 sets the busy signal at “0”, which indicates the processing unit 32 of the master device 3 is prepared to accept any further request.

[0125] Upon receipt of the request for transmitting the request-acceptance, the response-transmitting unit 33 generates a response message 60 including the response command 61 of “0” which indicates that any further request is acceptable to the master device 3 and that the request [Rb] has been processed and transmits the response message 60 through the inter-coupling network 2 to the slave device 1-2 for giving the slave device 1-2 a notice to the effect that the request [Rb] has been processed by the master device 3 and any further request is acceptable to the master device 3.

[0126] In the step S31 of FIG. 9, the response-receiving unit 12 of the slave device 1-2 receives the response message 60 including the response command 61 of “0”. In the step S32 of FIG. 9, the response-receiving unit 12 sends a request-enable signal to the request transmitting unit 11 for enabling the request transmitting unit 11 to issue or transmit any further request.

[0127] During the processings to the request [Rb] by the processing unit 32, the busy signal is maintained at “1” which indicates that the processing unit 32 is busy and placed in the currently-processing state which does not accept no further request. It is assumed that during the busy state “1” of the busy signal, the slave device 1-3 re-issues the request [Rc]. In the step S1 of FIG. 6, the request-receiving unit 31 receives the request [Rc], whilst in the steps S2 and S3 of FIG. 6, the busy signal is “1” and the retry flag is “1”. In the step S4 of FIG. 6, the processing unit 32 sends the response-transmitting unit 33 a request for issuing the notice of rejection to the request [Rc], wherein the retry identification 62 becomes “1” identical with “1” of the retry identification 52 included in the request message 50.

[0128] The response-transmitting unit 33 receives the request for issuing the notice of rejection to the request [Rc], and transmits the response message 60 including the retry identification 62 at “1” and the response command 61 at “1” through the inter-coupling network 2 to the slave device 1-3 which had issued the rejected request [Rc].

[0129] In the step S31 of FIG. 9, the response-receiving unit 12 of the slave device 1-3 receives the response message 60 including the retry identification 62 at “1” and the response command 61 at “1” which indicates that the request [Rb] was rejected by the master device 3. In the step S33 of FIG. 9, the response-receiving unit 12 sends the request transmitting unit 11 a request for re-transmitting the request [Rc]. The request transmitting unit 11 receives the request for re-transmitting the request [Rc] from the response-receiving unit 12. In the steps S23 and S24 of FIG. 8, the request transmitting unit 11 sets the retry flag 51 at “1” and the retry identification 52 at “1” in accordance with “1” of the retry identification 62 included in the received response message 60. The request transmitting unit 11 re-transmits or re-issues the request [Rc] through the inter-coupling network 2 to the master device 3.

[0130] After the processing to the prior request [Rb] by the processing unit 32 of the master device 3 has been completed, then the processing unit 32 sets the busy signal at “0”. It is assumed that the request-receiving unit 31 holds the reservation number “2” and the service number “1”, and further the slave device 1-3 re-issues the once rejected request [Rc], wherein the request [Rc] includes the retry flag “1” and the retry identification “1”. The request [Rc] is also transmitted through the inter-coupling network 2 to the master device 3.

[0131] In the step S1 of FIG. 6, the request-receiving unit 31 of the master device 3 receives the request [Rc] re-issued from the slave device 1-3. In the step S2 of FIG. 6 and the steps S6 and S7 of FIG. 7, the busy signal is “0”, the retry flag is 1 and the service number and the reservation number take the same value “1”. In the step S8 of FIG. 7, the request [Rc] is transmitted from the request-receiving unit 31 to the processing unit 32. The processing unit 32 receives the request [Rc] and enters into the processing state, during which the busy signal is maintained at “1”, which indicates the processing unit 32 of the master device 3 is busy and placed in the currently-processing state which does not accept no further request. The current service number “1” is incremented to “2” in the step S8 of FIG. 7.

[0132] After the processing unit 32 completes the processings to the request [Rb], then the processing unit 32 sends the response-transmitting unit 33 a request for transmitting the request-acceptance. After the response-transmitting unit 33 received the request for transmitting the request-acceptance, then the processing unit 32 sets the busy signal at “0” which indicates the processing unit 32 of the master device 3 is prepared to accept any further request.

[0133] Upon receipt of the request for transmitting the request-acceptance, the response-transmitting unit 33 generates a response message 60 including the response command 61 of “0” which indicates that any further request is acceptable to the master device 3 and that the request [Rc] has been processed and transmits the response message 60 through the inter-coupling network 2 to the slave device 1-2 for giving the slave device 1-3 a notice to the effect that the request [Rc] has been processed by the master device 3 and any further request is acceptable to the master device 3.

[0134] In the step S31 of FIG. 9, the response-receiving unit 12 of the slave device 1-3 receives the response message 60 including the response command 61 of “0”. In the step S32 of FIG. 9, the response-receiving unit 12 sends a request-enable signal to the request transmitting unit 11 for enabling the request transmitting unit 11 to issue or transmit any further request.

[0135] Consequently, the master device is adopted to give priorities to respective requests in the sequence of the first receiving times from the plural slave devices, wherein the given priorities of the respective requests accord to the sequence of the first receiving times thereof, so that the master device determines the sequences of processings based on the respectively given priorities for allowing the master device to decide to process the highest priority one of the requests, whereby the master device remains to reject any lower priority given requests or no priority given request which is first received, regardless of the busy or non-busy state, until the master device receives the highest priority given request in the non-busy time and completes the proceeding to the highest priority given request. Since the priority level depend on the first receiving time or the receipt sequence of the request message which have been rejected by the master device due to its busy state or lower priority level than that of one or more other request messages, this may prevents any undesirable stubbation or deadlock situation in which processing to the request message by the master device is suspended, without using any buffer in the master device.

[0136] Modification

[0137] The above described novel feature of the system in accordance with the first embodiment of the present invention may optionally be applied to another system which includes a plurality of service-providing devices such as master devices and a plurality of service-requesting devices such as slave devices which are also accessible to the plurality of service-providing devices such as master devices through any available coupling medium such as an inter-coupling network.

[0138]FIG. 10 is a block diagram illustrative of a novel service system in accordance with the modified embodiment of the present invention. The service system includes a plurality of master devices 4-1, 4-2, - - - 4-M as servers for providing services and a plurality of slave devices 1-1, 1-2, - - - 1-n as clients for requesting the master devices 4-1, 4-2, - - - 4M to provide the services in response to the issued requests, wherein the plurality of slave devices 1-1, 1-2, - - - 1-n are coupled to the master devices 4-1, 4-2, - - - 4-M through the inter-coupling network 2. The plurality of slave devices 1-1, 1-2, - - - 1-n have a uniform or common internal configuration as described above and shown in FIG. 2. The plurality of master devices 4-1, 4-2, - - - 4-M have a uniform or common internal configuration as described above and shown in FIG. 3. The following descriptions will focus on the difference of this modified embodiment from the above first embodiment.

[0139] The each slave device 1 selects one of the plural master devices 4-1, 4-2, - - - 4-M for transmitting the request thereto. If the request is rejected by the selected master device 4-i, then the each slave device 1 re-transmits the rejected request to the selected master device 4-i which requested the request.

[0140] It is assumed that the each master device 4-i has a respective maximum request number “m_(i)” which indicates the maximum number of the requests acceptable to the each master device 4-i. The request-receiving unit 31 of the each master device 4-i holds reservation numbers and service numbers, each of which may be generated by using a counter which is operable to count the number not less than “m_(i)”.

[0141] The retry identification 52 included in the request message 50 comprises the necessary bit number which is capable of representing the maximum value of the respective maximum request numbers “m₁”, “m₂” - - - “m_(i)” - - - “m_(M)” of the master devices 4-1, 4-2, - - - 4-i, - - - 4-M. The retry identification 62 included in the response message 60 also comprises the necessary bit number which is capable of representing the maximum value of the respective maximum request numbers “m₁”, “m₂” - - - “m_(i)” - - - “m_(M)” of the master devices 4-1, 4-2, - - - 4-i, - - - 4-M.

[0142] It is appreciated that each of the retry identification 52 included in the request message 50 and the retry identification 62 included in the response message 60 comprises the necessary minimum bit member. It is assumed that the master device 3 of the first embodiment and the master devices 4-1, 4-2, - - - 4-i, - - - 4-M of the modified embodiment have the maximum request number “m”. The request-receiving unit 31 of the master device 3 in the first embodiment needs the ring-counter of j-bits (m≦2i) for holding the reservation number and the service number. The ring-counter of j-bits (m≦2i) is also needed for the retry identifications 52 and 62 of the request and response messages 50 and 60 respectively.

[0143] In the modified embodiment, the retry identifications 52 and 62 of the request and response messages 50 and 60 respectively may be represented in g-bits (g<j). The request-receiving unit 31 of the master devices 4-1, 4-2, - - - 4-i, - - - 4-M of the modified embodiment needs the ring-counter of 1-bits (m+2^((1−g))≦2¹) for holding the reservation number and the service number. In this case, the operations are different from what was described in the first embodiment in connection with the operations of the request-receiving unit 31 and the response-transmitting unit 33. For the operation of the request-receiving unit 31, the service number is the i-bits, whilst the retry identification 52 of the request message 50 is the g-bits, for which reason the higher significant bits “g” in the 1-bits of the service number are compared to the retry identification 52 of the g-bits. For the operations of the response-transmitting unit 33, if the response-transmitting unit 33 sends the notice that the request message 50 including the retry flag 51 at “0” was rejected by the processing unit 32, then the response-transmitting unit 33 sets the retry identification 62 of the response message 60 on the basis of the reservation number. In the first embodiment, the retry identification 62 of the response message 60 is set identical with the value of the reservation number. In the modified embodiment, the retry identification 62 of the response message 60 is set identical with the higher significant g-bits of the reservation number. If the response-transmitting unit 33 sends the notice that the request message 50 including the retry flag 51 at “1” was rejected by the processing unit 32, then the retry identification 62 of the response message 60 is set identical with the value of the reservation number.

[0144] Although the invention has been described above in connection with several preferred embodiments therefor, it will be appreciated that those embodiments have been provided solely for illustrating the invention, and not in a limiting sense. Numerous modifications and substitutions of equivalent materials and techniques will be readily apparent to those skilled in the art after reading the present application, and all such modifications and substitutions are expressly understood to fall within the true scope and spirit of the appended claims. 

What is claimed is:
 1. A system for providing services, including: a plurality of slave device for issuing respective request message; and at least a master device allowing respective access from said plurality of slave device and processing said request message in response to said respective request message in order to provide a response message to one of said plurality of slave device, which issued said request message; wherein said master device is adopted to recognize a priority-related information of said request message for processing said request message, and said priority-related information includes: a first information indicating whether said request message is first received or has been received in the past but rejected for processing; and a second information indicating a receipt sequence of said request message.
 2. The system as claimed in claim 1, wherein said master device further includes: a process-deciding unit for recognizing said priority-related information to decide, whether said request message should promptly be processed or be rejected, with reference to said priority-related information; a processing unit for processing said request message; and a response unit for issuing said response message together with said second information and a third information indicating whether said request message has been processed or rejected.
 3. The system as claimed in claim 2, wherein each of said plurality of slave device further includes: a request issuing unit for issuing said request message; and a response receiving unit for receiving said response message together with said second information and said third information and requesting said request issuing unit to re-issue said request message if said third information indicates that said request message has been rejected.
 4. The system as claimed in claim 2, wherein said processing unit issues, to said process-deciding unit, a fourth information indicating whether said processing unit is in an acceptable state which allows said processing unit to promptly process said request message or in an unacceptable state which inhibits said processing unit to promptly process said request message, so that said process-deciding unit decides, whether said request message should promptly be processed or be rejected, with reference to said fourth information in addition to said priority-related information.
 5. The system as claimed in claim 4, wherein said process-deciding unit is adopted to hold therein a reservation number indicating a reservation order and a service number indicating a service order for said request message separately from said request message and said response message.
 6. The system as claimed in claim 5, wherein said first information comprises a retry flag, said second information comprises a retry identification number, and said third information comprises a response command.
 7. The system as claimed in claim 6, wherein said retry identification number, said reservation number and said service number comprise the same bit number.
 8. The system as claimed in claim 7, wherein said process-deciding unit sends said request message to said processing unit for allowing said processing unit to process said request message and requests said response unit to issue said response message together with said third information indicating that said request message has been processed, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is identical with said service number, said process-deciding unit sets said response message with a retry identification number identical with said reservation number and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as makes an increment to said reservation number, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is not identical with said service number, said process-deciding unit sets said response message with a retry identification number identical with said retry identification number attached to said request message and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is not identical with said service number, said process-deciding unit sends said request message to said processing unit for allowing said processing unit to process said request message and requests said response unit to issue said response message together with said third information indicating that said request message has been processed as well as makes an increment to said service number, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is identical with to said service number, said process-deciding unit sets said response message with a retry identification number identical with said reservation number and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as makes an increment to said reservation number, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said unacceptable state, and said retry flag indicates that said request message is first received, and said process-deciding unit sets said response message with a retry identification number identical with said retry identification number attached to said request message and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said unacceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing.
 9. The system as claimed in claim 6, wherein said reservation number and said service number comprise the same bit number, and said retry identification number comprises a less bit number than said reservation number and said service number.
 10. The system as claimed in claim 9, wherein said process-deciding unit sends said request message to said processing unit for allowing said processing unit to process said request message and requests said response unit to issue said response message together with said third information indicating that said request message has been processed, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is identical with to said service number, said process-deciding unit sets said response message with a retry identification number identical with corresponding higher significant bits of said reservation number to said less bit number of said retry identification number, and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as makes an increment to said reservation number, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is not identical with said service number, said process-deciding unit sets said response message with a retry identification number identical with said retry identification number attached to said request message and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is not identical with corresponding higher significant bits of said service number to said less bit number of said retry identification number, said process-deciding unit sends said request message to said processing unit for allowing said processing unit to process said request message and requests said response unit to issue said response message together with said third information indicating that said request message has been processed as well as makes an increment to said service number, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is identical with corresponding higher significant bits of said service number, said process-deciding unit sets said response message with a retry identification number identical with said corresponding higher significant bits of said reservation number and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as makes an increment to said reservation number, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said unacceptable state, and said retry flag indicates that said request message is first received, and said process-deciding unit sets said response message with a retry identification number identical with said retry identification number attached to said request message and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said unacceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing.
 11. The system as claimed in claim 1, wherein said at least master device comprises a plurality of master device.
 12. The system as claimed in claim 11, wherein said slave device is adopted to select one of said plurality of master device for issuing said message request at first time to said selected one of said plurality of master device, and also to re-issue said message request to said selected one of said plurality of master device if said request message has been rejected by said selected one of said plurality of master device.
 13. A system for providing services, including: a plurality of slave device for issuing respective request message; and at least a master device allowing respective access from said plurality of slave device and processing said request message in response to said respective request message in order to provide a response message to one of said plurality of slave device, which issued said request message; wherein said master device is adopted to give a priority-related information to said response message in response to said request message if said master device rejects said request message without processing said request message, and said priority-related information includes: a first information indicating whether said request message is first received or has been received in the past but rejected for processing; and a second information indicating a receipt sequence of said request message.
 14. The system as claimed in claim 13, wherein said master device further includes: a process-deciding unit for recognizing said priority-related information to decide, whether said request message should promptly be processed or be rejected, with reference to said priority-related information; a processing unit for processing said request message; and a response unit for issuing said response message together with said second information and a third information indicating whether said request message has been processed or rejected.
 15. The system as claimed in claim 14, wherein each of said plurality of slave device further includes: a request issuing unit for issuing said request message; and a response receiving unit for receiving said response message together with said second information and said third information and requesting said request issuing unit to re-issue said request message if said third information indicates that said request message has been rejected.
 16. The system as claimed in claim 14, wherein said processing unit issues, to said process-deciding unit, a fourth information indicating whether said processing unit is in an acceptable, state which allows said processing unit to promptly process said request message or in an unacceptable state which inhibits said processing unit to promptly process said request message, so that said process-deciding unit decides, whether said request message should promptly be processed or be rejected, with reference to said fourth information in addition to said priority-related information.
 17. The system as claimed in claim 16, wherein said process-deciding unit is adopted to hold therein a reservation number indicating a reservation order and a service number indicating a service order for said request message separately from said request message and said response message.
 18. The system as claimed in claim 17, wherein said first information comprises a retry flag, said second information comprises a retry identification number, and said third information comprises a response command.
 19. The system as claimed in claim 18, wherein said retry identification number, said reservation number and said service number comprise the same bit number.
 20. The system as claimed in claim 19, wherein said process-deciding unit sends said request message to said processing unit for allowing said processing unit to process said request message and requests said response unit to issue said response message together with said third information indicating that said request message has been processed, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is identical with said service number, said process-deciding unit sets said response message with a retry identification number identical with said reservation number and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as makes an increment to said reservation number, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is not identical with said service number, said process-deciding unit sets said response message with a retry identification number identical with said retry identification number attached to said request message and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is not identical with said service number, said process-deciding unit sends said request message to said processing unit for allowing said processing unit to process said request message and requests said response unit to issue said response message together with said third information indicating that said request message has been processed as well as makes an increment to said service number, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is identical with to said service number, said process-deciding unit sets said response message with a retry identification number identical with said reservation number and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as makes an increment to said reservation number, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said unacceptable state, and said retry flag indicates that said request message is first received, and said process-deciding unit sets said response message with a retry identification number identical with said retry identification number attached to said request message and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said unacceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing.
 21. The system as claimed in claim 18, wherein said reservation number and said service number comprise the same bit number, and said retry identification number comprises a less bit number than said reservation number and said service number.
 22. The system as claimed in claim 21, wherein said process-deciding unit sends said request message to said processing unit for allowing said processing unit to process said request message and requests said response unit to issue said response message together with said third information indicating that said request message has been processed, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is identical with to said service number, said process-deciding unit sets said response message with a retry identification number identical with corresponding higher significant bits of said reservation number to said less bit number of said retry identification number, and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as makes an increment to said reservation number, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is not identical with said service number, said process-deciding unit sets said response message with a retry identification number identical with said retry identification number attached to said request message and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is not identical with corresponding higher significant bits of said service number to said less bit number of said retry identification number, said process-deciding unit sends said request message to said processing unit for allowing said processing unit to process said request message and requests said response unit to issue said response message together with said third information indicating that said request message has been processed as well as makes an increment to said service number, if said fourth information indicates that said processing unit is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is identical with corresponding higher significant bits of said service number, said process-deciding unit sets said response message with a retry identification number identical with said corresponding higher significant bits of said reservation number and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as makes an increment to said reservation number, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said unacceptable state, and said retry flag indicates that said request message is first received, and said process-deciding unit sets said response message with a retry identification number identical with said retry identification number attached to said request message and requests said response unit to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without sending said request message to said processing unit, if said fourth information indicates that said processing unit is in said unacceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing.
 23. The system as claimed in claim 13, wherein said at least master device comprises a plurality of master device.
 24. The system as claimed in claim 23, wherein said slave device is adopted to select one of said plurality of master device for issuing said message request at first time to said selected one of said plurality of master device, and also to re-issue said message request to said selected one of said plurality of master device if said request message has been rejected by said selected one of said plurality of master device.
 25. A method of controlling a system for providing services including: a plurality of slave device for issuing respective request message; and at least a master device allowing respective access from said plurality of slave device and processing said request message in response to said respective request message in order to provide a response message to one of said plurality of slave device, which issued said request message, wherein said method includes: recognizing a priority-related information of said request message for processing said request message, where said priority-related information includes: a first information indicating whether said request message is first received or has been received in the past but rejected for processing; and a second information indicating a receipt sequence of said request message.
 26. The method as claimed in claim 25, further including: allowing said at least master device to decide whether said request message should promptly be processed or be rejected, with reference to said priority-related information; allowing said at least master device to process said request message; and allowing said at least master device to issue said response message together with said second information and a third information indicating whether said request message has been processed or rejected.
 27. The method as claimed in claim 26, further including: allowing each of said plurality of slave device to issue said request message; and allowing each of said plurality of slave device to receive said response message together with said second information and said third information and to re-issue said request message if said third information indicates that said request message has been rejected.
 28. The method as claimed in claim 26, further including: allowing said at least master device to hold a fourth information indicating whether said at least master device is in an acceptable state which allows said at least master device to promptly process said request message or in an unacceptable state which inhibits said at least master device to promptly process said request message, so that said at least master device decides, whether said request message should promptly be processed or be rejected, with reference to said fourth information in addition to said priority-related information.
 29. The method as claimed in claim 28, further including: allowing said at least master device hold therein a reservation number indicating a reservation order and a service number indicating a service order for said request message separately from said request message and said response message.
 30. The method as claimed in claim 29, wherein said first information comprises a retry flag, said second information comprises a retry identification number, and said third information comprises a response command.
 31. The method as claimed in claim 30, wherein said retry identification number, said reservation number and said service number comprise the same bit number.
 32. The method as claimed in claim 31, further including: allowing said at least master device to process said request message and issue said response message together with said third information indicating that said request message has been processed, if said fourth information indicates that said at least master device is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is identical with said service number, allowing said at least master device to set said response message with a retry identification number identical with said reservation number and requests said response unit and to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as to make an increment to said reservation number, without processing said request message, if said fourth information indicates that said at least master device is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is not identical with said service number, allowing said at least master device to set said response message with a retry identification number identical with said retry identification number attached to said request message and to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without processing said request message, if said fourth information indicates that said at least master device is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is not identical with said service number, allowing said at least master device to process said request message and to issue said response message together with said third information indicating that said request message has been processed as well as to make an increment to said service number, if said fourth information indicates that said at least master device is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is identical with to said service number, allowing said at least master device to set said response message with a retry identification number identical with said reservation number and to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as to make an increment to said reservation number, without processing said request message, if said fourth information indicates that said at least master device is in said unacceptable state, and said retry flag indicates that said request message is first received, and allowing said at least master device to set said response message with a retry identification number identical with said retry identification number attached to said request message and to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without processing said request message, if said fourth information indicates that said at least master device is in said unacceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing.
 33. The method as claimed in claim 30, wherein said reservation number and said service number comprise the same bit number, and said retry identification number comprises a less bit number than said reservation number and said service number.
 34. The method as claimed in claim 33, further including: allowing said at least master device to process said request message and to issue said response message together with said third information indicating that said request message has been processed, if said fourth information indicates that said at least master device is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is identical with to said service number, allowing said at least master device to set said response message with a retry identification number identical with corresponding higher significant bits of said reservation number to said less bit number of said retry identification number, and to issue said response message together with staid retry identification number and said third information indicating that said request message has been rejected as well as to make an increment to said reservation number, without processing said request message, if said fourth information indicates that said at least master device is in said acceptable state, and said retry flag indicates that said request message is first received, and said reservation number is not identical with said service number, allowing said at least master device to set said response message with a retry identification number identical with said retry identification number attached to said request message and to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without processing said request message, if said fourth information indicates that said at least master device is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is not identical with corresponding higher significant bits of said service number to said less bit number of said retry identification number, allowing said at least master device to process said request message and to issue said response message together with said third information indicating that said request message has been processed as well as to make an increment to said service number, if said fourth information indicates that said at least master device is in said acceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing, and said retry identification number is identical with corresponding higher significant bits of said service number, allowing said at least master device to set said response message with a retry identification number identical with said corresponding higher significant bits of said reservation number and to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected as well as to make an increment to said reservation number, without processing said request message, if said fourth information indicates that said at least master device is in said unacceptable state, and said retry flag indicates that said request message is first received, and allowing said at least master device to set said response message with a retry identification number identical with said retry identification number attached to said request message and to issue said response message together with said retry identification number and said third information indicating that said request message has been rejected, without processing said request message, if said fourth information indicates that said at least master device is in said unacceptable state, and said retry flag indicates that said request message has been received in the past but rejected for processing.
 35. The method as claimed in claim 25, wherein if said at least master device comprises a plurality of master device, one of said plurality of master device is selected by said slave device for issuing said message request at first time to said selected one of said plurality of master device, and also for re-issuing said message request to said selected one of said plurality of master device if said request message has been rejected by said selected one of said plurality of master device. 